2,914 research outputs found
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Validation of data analysis routines for a thermal probe apparatus using numerical data sets
Most thermal properties of construction materials used in the analysis of building performance have been measured under laboratory conditions, using a guarded hot box or hot plate apparatus. As a consequence, these properties seldom reflect the impact of actual conditions (especially moisture content) on the values of conductivity and diffusivity. Hence there is a need to develop techniques that allow to take into account local conditions, and measure building material properties in situ. One option available is the use of a thermal probe. The thermal probe technique is based on creating a line source in a material sample, and measuring the temperature rise in the sample in reaction to heat being applied. Obviously the data analysis routines used to calculate thermal conductivity and thermal diffusivity based on the temperature rise observed are crucial to the success of the technique. Transient thermal simulation of a of a model representing a line source in an infinite material sample has been used to generate a set of numerical data sets to validate analysis routines in conjunction with an experimental thermal probe apparatus. Findings show that by careful application of these routines, a close agreement with simulation input values can be achieved, with errors of less than one percent. This validates the analysis routines and provides a deeper appreciation of the theoretical behaviour of a thermal probe
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An assessment of the potential returns of energy certificates for the UK household sector
Purpose – This article seeks to investigate the interconnections between the expectations of the impact of energy certificates issued within the UK domestic building sector through the Energy Performance of Buildings Directive (EPBD) and the actual number and financial implications of the energy saving measures (ESMs) achieved. Design/methodology/approach – The methodology uses two previously published surveys and compares these with a third independent survey by the authors focusing upon the discrepancies between planned action and implemented action, introducing the term human factor element (hfe). Findings – The article concludes that annual carbon savings arising from implementation of the Energy Performance Certificate (EPC) may be as low as 73.4?ktC over the five year term of the Kyoto Protocol even though 44 per cent of energy saving measure costs of £200 million are recouped within the same time period and savings will continue for up to 40 years. Achieving annual savings of only 14.7?ktC by 2010, such a figure represents a mere 0.3 per cent of the annual domestic 4.8?MtC savings announced by the government in its 2006 Climate Change Programme. Practical implications – Since the principal determinant in the uptake of ESMs is initial cost, it is considered that the EPBD is likely to remain an under-performing instrument in the promotion of energy sufficiency until such time as other complementary provisions are introduced. Originality/value – Sheds light upon the likely financial impact upon energy efficiency in domestic buildings by energy certificates
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Thermal probe technology for buildings: the transition from laboratory to field measurements
This article reports the results of an investigation into the transfer of thermal probe measurement technology from laboratory use to actual buildings in order to undertake the in situ determination of thermal material properties. The imperative for using in situ measurements is 1) the impact of moisture content on thermal properties, 2) the possible wide range of variation of properties across most materials used in construction, and 3) the lack of data for new and innovative materials. Thermal probe technology offers the prospect of taking building specific data, addressing these issues. Based on commercially available thermal probes a portable measurement kit and accompanying measurement procedure have been developed. Three case study buildings, each having different materials, have been studied to ascertain whether or not the technique can be transferred to relatively uncontrolled environments while remaining capable of achieving a precision that is similar to an ASTM standard that can be related to thermal conductivity measurements of building materials. The results show that this is indeed the case, and that the use of thermal probe technology may yield thermal properties that vary significantly from the laboratory values currently used in building thermal engineering calculations
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Measured indoor temperatures, thermal comfort and overheating risk: Post-occupancy evaluation of low energy houses in the UK
There is growing concern in Western Europe that higher insulation and air tightness of residential buildings leads to increased overheating risk. This paper discusses temperature monitoring from identical houses in the Southwest of the UK that were built to low energy standards (Code for Sustainable Homes Level 5). The temperature data were analysed using both established static overheating criteria (CIBSE Guide A) and an adaptive thermal comfort standard (BSEN15251). The houses can be considered uncomfortably warm during summer and are at risk of overheating. The study suggests that occupant behaviour plays an important role in reducing or increasing internal temperatures
Extending the UK's green deal with the consideration of occupant behaviour
This paper introduces a study, which extends the current UK’s Green Deal through a consideration of modifying occupant behaviour in buildings to save building energy consumption. A case study was carried out in a typical mid-terraced residential building located in the Southwest of the UK. In the study, dynamic building performance simulation was used to predict the energy saving potential of various behaviour change options so as to help occupants use the building more energy efficiently. Feedback from building occupants reveals that this approach is helpful in reducing energy demand in a real building application, but also points out the need for future work
Building defect detection: External versus internal thermography
publisher: Elsevier articletitle: Building defect detection: External versus internal thermography journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2016.06.011 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved
The squashed entanglement of the noiseless quantum Gaussian attenuator and amplifier
We determine the maximum squashed entanglement achievable between sender and
receiver of the noiseless quantum Gaussian attenuators and amplifiers and we
prove that it is achieved sending half of an infinitely squeezed two-mode
vacuum state. The key ingredient of the proof is a lower bound to the squashed
entanglement of the quantum Gaussian states obtained applying a two-mode
squeezing operation to a quantum thermal Gaussian state tensored with the
vacuum state. This is the first lower bound to the squashed entanglement of a
quantum Gaussian state and opens the way to determine the squashed entanglement
of all quantum Gaussian channels. Moreover, we determine the classical squashed
entanglement of the quantum Gaussian states above and show that it is strictly
larger than their squashed entanglement. This is the first time that the
classical squashed entanglement of a mixed quantum Gaussian state is
determined
The Thermal Performance Prospects of Courtyards in Cold Conditions
Aiming at developing more thermally comfortable and energy efficient buildings,
some studies have been advocating using traditional architecture’s passive design strategies.
Among the rarely investigated architectural elements to achieve this objective in cold climates
is the courtyard space. This environmental element, in most cases, has been examined and
suggested for hot conditions. However, some studies have shown indications of its potential
environmental efficiency in cold conditions as well. In principle, courtyards enable having
sheltered outdoor spaces to regulate indoor spaces’ interaction with the outdoor climate instead
of having them outward oriented to directly face outdoor conditions. This research aims to
determine whether this thermal performance of courtyards can be positive in cold conditions as
it is in hot conditions, for instance, through protecting buildings from cold winds. To achieve
this objective, the research conducted simulation experiments to determine the thermal
conditions of 360 different courtyards and compared them with a typical modern urban outdoor
space’s conditions. If the courtyard space offers a warmer environment than modern urban
outdoor spaces, then it might lead to a wider positive impact on buildings’ thermal conditions
and energy consumption. The used simulation tool to conduct the simulation experiments is
Envi-met 4.2, which has been widely used and validated by previous simulation studies. The
tested courtyard forms are of different geometric configurations to show a wide range of possible
conditions in courtyards. The simulation was done for Baghdad, in which courtyards have been
widely used for centuries. This city has a hot summer, but its winter temperature is between 0°C
and 12°C. The Globe Temperature was used to determine peoples’ thermal sensation. Its value
includes the impact of air velocity, radiation and air temperature, which makes it representing
people’s actual thermal sensation properly. The results showed that courtyards offer higher
Globe Temperature than modern urban spaces in cold conditions, mainly, through protecting
buildings and occupants from winds. The air velocity inside courtyards can be one-tenth of air
velocity in a modern urban outdoor space. The geometric properties of courtyards significantly
affect courtyards’ thermal conditions. These results indicate that the courtyard space can be more
thermally efficient than modern urban spaces even in cold climate conditions. However, its
geometric properties need to be properly considered to have its highest possible thermal
efficiency. Otherwise, the courtyard might lose its efficient thermal performance
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